The demand for high data rates in mobile communications and the rapid increase in the number of cellular consumers has led to an aggressive reuse of frequencies, which increases the co-channel interference between adjacent cells. Such interference degrades system throughput, particularly to cell edge users. Coordinated multi-point (CoMP) transmission, in which adjacent smart-remote radio heads (S-RRH), or base stations (BSs), coordinate their transmission and jointly form a cluster which serves several mobile stations, is a known method for mitigating co-channel interference. One scheme of CoMP, employing joint processing (JP), is based on transforming the interference into a useful signal. JP however requires a large transmission overhead for sharing channel state information (CSI) between the S-RRHs that form the cluster.
Fifth generation (5G) mobile communication standards include architectural modifications that facilitate inter-cell cooperation. For example, in the cloud radio access network (C-RAN) architecture, a centralized base band unit (BBU) is connected via high data-rate links, dubbed the front-haul, to a large number of remote radio heads (RRHs). RRHs typically have some local processing capability and are called smart RRHs (S-RRHs). The BBU typically includes multiple base transceiver stations and therefore may also be referred to as a BBU pool.
Although an architecture of S-RRHs communicating to the BBU allows for some inter-cell cooperation, it does not support the level of cooperation required for JP. This is because in JP, the CSI must be quantized, fed back to the BBU, and processed in order to calculate a joint pre-coding matrix, which must then be quantized and fed back to the corresponding S-RRH. When all communications is through the BBU, the process generally cannot be done within a few milliseconds, which means that the CSI becomes outdated.